首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   12108篇
  免费   880篇
  国内免费   871篇
  13859篇
  2024年   39篇
  2023年   217篇
  2022年   327篇
  2021年   380篇
  2020年   378篇
  2019年   580篇
  2018年   593篇
  2017年   329篇
  2016年   366篇
  2015年   404篇
  2014年   674篇
  2013年   971篇
  2012年   470篇
  2011年   698篇
  2010年   542篇
  2009年   555篇
  2008年   605篇
  2007年   647篇
  2006年   527篇
  2005年   489篇
  2004年   384篇
  2003年   314篇
  2002年   340篇
  2001年   338篇
  2000年   238篇
  1999年   187篇
  1998年   198篇
  1997年   203篇
  1996年   171篇
  1995年   165篇
  1994年   143篇
  1993年   112篇
  1992年   99篇
  1991年   99篇
  1990年   97篇
  1989年   83篇
  1988年   63篇
  1987年   71篇
  1986年   63篇
  1985年   95篇
  1984年   113篇
  1983年   84篇
  1982年   99篇
  1981年   71篇
  1980年   39篇
  1979年   57篇
  1978年   47篇
  1977年   38篇
  1976年   30篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Stephanie Fanucchi 《FEBS letters》2009,583(22):3557-3562
A novel survival role of focal adhesion kinase (FAK) that involves its nuclear translocation and direct association with p53 has been demonstrated. Here we examined the relationship between the p53/FAK interaction and Ser46 phosphorylation of p53 (p-p53Ser46) in the apoptotic regulation of human esophageal squamous cell carcinoma (HOSCC) cell lines, expressing either wild type (wt) p53 or mutant (mt) p53-R175H. In contrast to the wt p53 cell lines, the mt p53-R175H cell line was resistant to staurosporine (STS)-mediated detachment and caspase-3 activation. Furthermore, despite the resistance of mt p53-R175H to Ser46 phosphorylation, both wt and mt HOSCC cells translocate FAK into the nucleus and maintain the p53/FAK interaction post STS treatment. These findings provide unique insight into how tumor cells harboring the R175H mutant may resist chemotherapeutic intervention.

Structured summary

MINT-7294020: FAK (uniprotkb:Q05397) physically interacts (MI:0915) with p53 (uniprotkb:P04637) by anti-bait coimmunoprecipitation (MI:0006)  相似文献   
82.
Ecological restoration is practiced by people of diverse backgrounds working at many different levels in a variety of settings. Portraying the human body as a metaphor of a natural ecosystem can be useful in identifying the breadth of strategies used to restore the natural environment. A technical approach, environmental stewardship, and more spiritual traditional attitudes to ecological restoration can be viewed as analogous to restoring health to the human body through an operation in a hospital, administering remedies to oneself from the medicine cabinet, and taking a broader holistic/preventative approach to cultivate the mind–body connection through, e.g., yoga.  相似文献   
83.
Sanna Ojalammi 《Anthrozo?s》2018,31(2):233-246
These days zoos often claim that their main objective is the promotion of nature conservation and that they strive to educate their visitors about animals and nature conservation. But how do zoo visitors themselves perceive this emphasis on conservation education? In order to determine how Helsinki Zoo visitors perceive nature conservation during their visit, we undertook a qualitative analysis of 75 structured situational interviews and five autoethnographical visits. Our results show that there was only a limited understanding of nature conservation among the zoo visitors. Their perception follows the typical framing of nature conservation in zoos: conservation projects that embrace captive breeding, in-situ conservation collaboration, and the reintroduction of those species. Moreover, in the Helsinki Zoo case these perceptions may have been influenced by the fact that the zoo did not give concrete advice on how the visitors themselves can contribute to conservation, except in terms of donating money. Framing nature conservation in such ways distances it from visitors’ everyday lives.  相似文献   
84.
85.
86.
87.
目的:研究重组人脑利钠肽(rh-BNP)联合阿托伐他汀治疗急性心梗后心衰的临床效果及对患者血清心肌肌钙蛋白(cardiac troponin,cTn-I)、肌红蛋白(Myoglobin,Myo)、肌酸激酶同工酶(CK-MB)水平的影响。方法:选择我院2017年2月~2019年1月收治的72例急性心梗后心衰患者,按随机数字表法分为观察组38例,对照组34例。对照组给予阿托伐他汀治疗,观察组在对照组基础上另加rh-BNP,观察和比较两组的临床疗效,治疗前后血清cTn-I、Myo、CK-MB水平的变化及治疗后不良反应的发生情况。结果:治疗后,观察组总有效率明显高于对照组(P0.05),血清cTn-I、Myo、CK-MB水平均显著低于对照组[(0.23±0.10) vs.(0.16±0.08)、(27.54±3.86) vs.(21.62±2.54)、(70.82±9.25) vs.(61.28±8.33)](P0.05)。观察组治疗后不良反情况总发生率为7.89%,明显低于对照组(26.47%,P0.05)。结论:与单用阿托伐他汀治疗相比,静脉注射rh-BNP联合阿托伐他汀治疗急性心梗后心衰可显著提高临床疗效和安全性,有效减低血清cTn-I、Myo、CK-MB水平。  相似文献   
88.
New trends in molecular medicine that have emerged owing to the success of the national Human Genome program are characterized. The major attention is paid to molecular diagnostics, preventive medicine, and gene therapy. Preventive medicine is a product of synthesis of the current notions on genetics and biochemistry of human diseases; it comprises pharmacogenetics, presymptomatic diagnosis, and testing of genes of predisposition to the most frequent multifactor diseases. In the Gene Therapy section, advantages and drawbacks of the main methods of delivery of nucleic acids into the cells are considered; diseases that are attempted to be rectified using gene therapy are listed. Exemplified with Duchenne myodystrophy, the problems encountered in correction of a genetic defect with the aid of foreign genes are considered. Results are summarized for assessing the efficiency of various methods of introduction of dystrophin cDNA (gene gun, liposomes, microspheres, viral oligopeptides, and lactoferrin) conducted on the Duchenne myodystrophy model, mdx mice.  相似文献   
89.
Chimpanzee erythrocytes express strong M but weak, occasional N blood-group activity, as detected by anti-M and anti-N reagents. We have found that the M activity is carried by a major membrane glycoprotein that is similar but not identical to the human MM glycoprotein (glycophorin A). We have isolated and characterized this glycoprotein from erythrocyte membranes of four individual chimpanzees. The purified glycoproteins strongly inhibited agglutination of M cells by rabbit anti-human M sera and only weakly inhibited the agglutination of N cells by rabbit anti-human N sera. They also displayed medium-to-strong inhibitory activity against chimpanzee iso- and crossimmune antisera tested with chimpanzee erythrocytes of various V-A-B-D and Wc specificities, which are known as chimpanzee extensions of the human type M-N system and the Miltenberger counterpart, respectively. Each glycoprotein was cleaved with CNBr into three fragments, whose size, solubility, and composition were analogous to those obtained by similar treatment of the human M-N antigens. The amino-terminal fragment was found to be a glycooctapeptide whose amino acid composition and partial sequence indicated that it is an intermediate form of the human M and N glycooctapeptides. Its carbohydrate content comprised two threonine-linked saccharide units that, although similar in composition to the human threonine-linked units, were fewer in number than the three units found in the corresponding human glycooctapeptides. Structural similarities to the human antigens strongly suggest that the amino terminus bears the major antigenic determinants of the molecule, and the occurrence in this region of numerous, albeit rare, variants among humans and in chimpanzees indicates that the corresponding coding sequence of the structural gene is particularly susceptible to mutational events. We conclude that the chimpanzee M gene product is a variant of the human type and that the chimpanzee gene is an allele of the human polymorphic M-N locus.This research was supported by National Institutes of Health Grants GM 16389 and HL 19011 and March of Dimes Grant 1-661.  相似文献   
90.

Background

Sodium octanoate (Oct) and N-acetyl-l-tryptophan (N-AcTrp) are widely used as stabilizers during pasteurization and storage of albumin products. However, exposure to light photo-degrades N-AcTrp with the formation of potentially toxic compounds. Therefore, we have examined the usefulness of N-acetyl-l-methionine (N-AcMet) in comparison with N-AcTrp for long-term stability, including photo stability, of albumin products.

Methods

Recombinant human serum albumin (rHSA) with and without additives was photo-irradiated for 4 weeks. The capability of the different stabilizers to scavenge reactive oxygen species (ROS) was examined by ESR spectrometry. Carbonyl contents were assessed by a spectrophotometric method using fluoresceinamine and Western blotting, whereas the structure of rHSA was examined by SDS-PAGE, far-UV circular dichroism and differential scanning calorimetry. Binding was determined by ultrafiltration.

Results

N-AcMet was found to be a superior ROS scavenger both before and after photo-irradiation. The number of carbonyl groups formed was lowest in the presence of N-AcMet. According to SDS-PAGE, N-AcMet stabilizes the monomeric form of rHSA, whereas N-AcTrp induces degradation of rHSA during photo-irradiation. The decrease in α-helical content of rHSA was the smallest in the presence of Oct, without or with N-AcMet. Photo-irradiation did not affect the denaturation temperature or calorimetric enthalpy of rHSA, when N-AcMet was present.

Conclusion

The weakly bound N-AcMet is a superior protectant of albumin, because it is a better ROS-protector and structural stabilizer than N-AcTrp, and it is probable and also useful for other protein preparations.

General significance

N-AcMet is an effective stabilizer of albumin during photo-irradiation, while N-Ac-Trp promotes photo-oxidative damage to albumin.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号